Use of quaternary ammonium compounds for stabilizing processed photographic elements



USE OF QUATERYARY AMMONIUM COMPGUNDS FOR STABILIZING PRUCESSED PHGTOGRAPHKC ELEMENTS Ismael A. Olivares and Delfin Galvez, Panama City, Panama, assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Dec. 12, 1958, Ser. No. 779,821

7 Claims. (Cl. 96-52) This invention relates to processes for stabilizing processed photographic elements against sufiding, image fading, and staining, and for preventing the growth of fungi, thereon.

In the processing of photographic developing-out materials such as gelatino-silver halide emulsions coated on paper, film, or glass supports, if, after fixation, the hypo I (usually sodium or ammonium thiosulfate) is not completley eliminated from the processed material by washing or other means, the silver image will tend to fade or change color under usual conditions of temperature and humidity during storage.

This fading is a result of the conversion of more or less of the silver image to silver sulfide by the sulfur present in the residual hypo. This is manifest by a change in hue of the image first to yellowish brown, then to yellow, and in most cases the change is accompanied by a yellowing of the unexposed portions of the image. This yellowing of the highlights is a result either of the use of an exhausted fixing bath, or insufficient fixation and washing, resulting in the retention of complex silversodium thiosulfates which under proper conditions decompose to give a yellow silver sulfide.

In addition to attack of the silver image by the sulfur bearing decomposition products of hypo within the gelatin layer, many external agents also attack the silver image, the most significant being hydrogen sulfide which is present in coal gas (illuminating gas). High humidity and temperature accelerate this reaction tremen dously. Sulfur dioxide and other acid gases in the presence of the hypo in the image layer also accelerate the fading of the image.

The rate at which a silver image fades depends upon many factors including (1) the concentration of hypo in the image layer, (2) the concentration of hydrogen sulfide and other gases in the atmosphere, (3) the grain size of the silver image and (4) the temperature and humidity of storage. Thus, a content of residual hypo as low as 0.005 milligram per square inch may cause fading with fine-grained images, especially in the case of photographic paper prints. Similarly, the combination of high humidity and high temperature which usually exists in tropical countries is fatal to a photographic print containing hypo.

The prevention of yellowing or fading of black-andwhite prints or films usually required the use heretofore of multiple fixing baths and prolonged washing, or the use of a complex oxidizing bath to chemically alter retained thiosulfate compounds to forms which were readily removable or which could not produce fading or yellowing. Oxidizing agents such as the hypochlorites, iodine, potassium permanganate, and hydrogen peroxide are all well known in photography but there are disadvantages in using each of them. For example, hypochlorites or potassium permanganate attack the images of fine grain materials, such as prints and fine grain films, when they are used in sufiicient concentrations and acidities to rapidly oxidize hypo. The same is true of iodine and, to a lesser extent, of hydrogen peroxide (in the absence of alkali) since they oxidize hypo principally to tetrathionate which, like hypo, can act as an agent in promoting image fading.

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In addition to the problem of fading, photographic elements, especially those containing gelatin, are quite subject to attack by fungus organisms when stored for periods of time under conditions of high temperature and humidity such as is common in tropical climates. Usually such fungus growths are very destructive to photographic prints or films.

It is, therefore, an object of the present invention to provide a new method for treating processed photographic elements which will effectively stabilize the photographic image against sulfiding and the resulting image fading and staining even when the elements contain appreciable residual sodium thiosulfate and/or silver thiosulfate comlex. A further object is to provide a method for stabilizing processed photographic elements which contain sodium thiosulfate and/or silver thiosulfate complex so that they do not fade or become stained during storage in tropical conditions. A further object is to provide a method for stabilizing processed photographic elements containing thiosulfate compounds without, at the same time, forming other compounds such as tetrathionate that also promote image fading. A further object is to provide a method of stabilizing processed photographic elements containing thiosulfate or a silver complex without using unstable oxidizing agents such as hydrogen peroxide. A still further object is to provide treatment for processed photographic elements which not only stabilizes the photographic image against fading and staining, but which also prevents the growth of fungus on the photographic element even when stored under tropical conditions. Other objects will be apparent from the description and claims which follow.

These and other objects are accomplished by means of this invention as described hereinafter. We have discovered a simple, rapid chemical treatment that effectively protects processed photographic elements against chemical and microbiological deterioration. The process embodying the invention is effected by treating a developed and fixed photographic element in an aqueous solution of a quaternary ammonium salt as defined herein, and then drying it without further Washing.

The process is characterized by using small quantities of chemicals which are nonvolatile, chemically stable, cheap, readily available, readily soluble in aqueous solution, colorless, safe to handle, and nontoxic to human beings. It does not require the use of multiple fixing baths, prolonged washing or the use of unstable chemicals such as hydrogen peroxide of the use of toxic chemicals such as iodine, potassium permanganate, etc. The process does not require that the fixing bath be fresh in order to prevent subsequent chemical deterioration of the photographic images produced. Exhausted fixing baths containing as much as 3 g. of silver per liter are used with excellent results in our process. Furthermore, the fix bath wash may be shortened from that required in other processes since it is not necessary in our process to remove all of the thiosulfate compounds from the photo: graphic material. In fact, it is actually desirable to have residual thiosulfate compounds in the image layer in order to get optimum stabilization of the photographic image.

Our process stabilizes the photographic element so that sulfiding with the resulting yellowing and image fading will not occur even after long periods of storage at the undesirably high temperatures and humidities normally found in the tropics. This protection is very effective against sulfiding that would normally occur from the decomposition of residual thiosulfate compounds in the image layer and also from the effect of exterior sulfiding agents which come into contact with the photographic element during long periods of storage. Not only is the treatment of our invention effective as a stabilizer against chemical deterioration but it also protects the treated prints or film against the attack of fungus and other microorganisms that are found in the temperature zones but are especially active and destructive in the tropics.

The quaternary ammonium salts which are used in the anti-sulfiding and fungicidal treatment emodying our invention are surface active agents having the formula:

e YK and wherein R, R R and R may be alkyl, aryloxyalkoxyalkyl, aryl, arylalkyl radicals in which there are usually 1 to 20 carbon atoms, and Z is a halogen atom or other anion such as sulfate or an acetate radical.

The quaternary ammonium salts which are usually employed have the formula:

R2 Z l V R 'O(CH2)2 o-"(CH2)2J I n; R; (A)

l/ x K (B) wherein R is an alkyl radical containing 6 to 20 carbon atoms, R is a hydrogen atom or lower alkyl radical containing 1 to 6 carbon atoms, R is an alkyl, aryl, or arylalkyl radical usually having 1 to 20 carbon atoms, R is an alkyl, aryl, or an arylalkyl radical usually having 7 to 16 carbon atoms, Z is a halogen atom such as chlorine, bromine, iodine, or fluorine, and n is or 1.

The compounds which we have found most useful and which are preferred for use in our invention have the Formula A wherein n is 1 and R is a benzyl radical, such as:

CH3 CH3 CH3 C1 CH: CH3 CH3 Dilsobutyl phenoxy ethoxy ethyl dimethyl benzyl ammonium chloride and CH3 CH3 J3EE Dlisobutyl cresoxy ethoxy ethyl dimethyl benzyl ammonium chloride Other compoundns within the scope of Formula A can also be used with good although somewhat less eflicacious results than the preferred compounds, or compounds of Formula B can be used with good results as typified by CH (CH) C] s \2 11/ Lauryl pyridinium chloride and C a( 2)1s C1 Cetyl pyridinium chloride Other compounds which also can be used in the treatment process of our invention include:

Cetyl dirnethyl benzyl ammonium chloride Cetyl trimethylammonium bromide Octadecyl amine acetate Lauryl trimethyl ammonium chloride Acetyl chlorine bromide Cetyl pyridinium fluoride We have found that these and other quaternary ammonium salts as defined herein can be used in the aqueous treatment bath in the concentration range of .25 to 5.0% by weight based on the vehicle with a preferred range of .25 to 2.0%. They are usually used at a concentration of 1%. Although the treatment baths usually contain a single quaternary ammonium salt, they may also contain combinations of them in Water or in water containing other materials to further condition the photographic element such as chemical buffering agents, formaldehyde, ethylene glycol and others.

The following examples illustrate typical uses of these compounds in our treatment baths.

EXAMPLE 1 Photographic paper prints were exposed, developed in a conventional manner, fixed in fresh acid fixer, washed for 5 minutes in water at 83 F., then soaked for 5 minutes in a 1% solution of diisobutyl phenoxy ethoxy ethyl dimethyl benzyl ammonium chloride and air dried. The prints were then subjected to 6 days storage under tropical conditions (98% relative humidity and F.). Prints which received this treatment were unchanged in appearance from those prepared in the same manner but held at normal room temperature and humidity. These results were surprising since control prints processed in the same manner but without the special treatment were severely faded and stained in image areas by the tropical storage.

EXAMPLE 2 Photographic prints were prepared and treated in the same manner as in Example 1 except that artifically exhausted (3 g. of Ag /l.) acid fixer was used in place of fresh acid fixer. Suprisingly, these prints showed no image fading and only a very slight yellowing in the nonimage area after 6 days storage under tropical conditions. Control prints showed severe fading and overall yellowing after the same tropical storage.

EXAMPLE 3 Paper prints were prepared and processed in the manner used in Example 1 but a 1% solution of diisobutyl cresoxy ethoxy ethyl dimethyl benzyl ammonium chloride was used in place of the 1% solution of the compound of Example 1. These prints were found to be unchanged following the 6 day storage at elevated temperatures and humidity in contrast with the severe fading and yellowing that was produced in a control print by the same tropical storage.

EXAMPLE 4 Paper prints were prepared and processed in the same manner as in Example 1 in which a 1% solution of lauryl pyridinium chloride was substituted for the 1% solution of the compound in Example 1. Six days storage at elevated temperature and humidity produced no stain or fading in these prints in contrast to the severe fading and staining produced in the control prints.

5 EXAMPLE 5 Twelve identical black-and-White prints were exposed from a normal negative. They were all given identical development in a conventional manner, then fixed, washed paper is used, it is advantageous to lengthen the u'sual5 minute treatment to 10 minutes.

Photographic black-and-whitc films, especially those coated with fine grain emulsions such as is commonly and treated as shown in Table I. After drying these 5 used for making miCYOCPPiBS f blue p l diiferently treated prints were exposed to accelerated aTe Stabilized Very effectively iflgamst Image g and fading tests by storing them at 110 F. and 98% RH fungal attack when they are given a 2 to minute treatfor six days. A comparison of the results shown in Table ment in a 1% solution of diisobutyl phenoxy ethoxy ethyl I shows the advantages derived from the treatment of our dimetllyl bBIIZYI ammonium Chloride following the invention. mal fixing bath Wash. A 1% solution of any of the other Table I ACCELERATED FADING TEST [Six days exposure at 110 F.; 98% R.H.]

Wash

Sample treated 5 minutes in a 1% solution of- Fixing conditions time, Control samples n id fixer) i Dnsobutyl phenoxy ethoxy Dusobutyl cresoxy ethoxy ethyl dimethyl benzyl ethyl dimethyl benzyl ammonium chloride ammonium chloride Fresh 5 Severe fading and staining in the Prints had normal appearance. Prints had normal appearance.

silver image area. Clear areas (No yellowing or fading ob- (No yellowing or fading observed.)

D0 Exhausted (3 gins. Ag+/l) Severe over-all yellowing.

Moderate over-all yellowing.

5 Severe fading in silver image area.

10 Slight fading in the silver image area.

N o fading observed. Very slight yelowing in the non-image area. o

served.)

Do. No fading observed. Very slight yelllowing in the non-image area.

EXAMPLE 6 Three identical black-and-white prints were exposed from a normal negative, developed in the conventional way, fixed in an artificially exhausted fixing bath and washed for five minutes. One print was then dried and used for a control. The other two prints were given a special five minute treatmentprior to drying; one being treated in a 1% solution of lauryl pyridinium chloride, the other being treated in a commercial hypo eliminator containing hydrogen peroxide, and ammonium hydroxide dissolved in water. Table II demonstrates the advantages of our treatment over no treatment or the use of a conventional hypo eliminator.

quaternary ammonium salts of our invention may also be used to advantage.

The treatment of our invention is most advantageously used in the protection of black-and-white prints and films because sulfiding is primarily detrimental to silver images. Although color pictures are not as subject to the detrimental effects of sulfiding as black-and-white pictures, since there is normally no silver image present, fungicidal protection is needed. The baths described can be used to advantage for the fungicidal protection they give.

Aqueous solutions of certain quaternary ammonium salts can be used very advantageously as a convenient and effective treatment bath for protecting photographic el Table II ACCELERATED FADING TEST [Six days exposure at 110 F.; 98% R.H.]

Sample treated for 5 minutes in- Wash Fixing conditions time Control samples (acid fixer) min.

1% solution of lauryl Hypo eliminator containing hydrogen pyridinium chloride peroxide, ammonium hydroxide in water solution Exhausted (3 gms. Ag+/1) 5 Severe fading in the silver image area.

Severe over-all yellowing-.-

No fading observed No appreciable yellowing Considerable fading observed.

Slight over-all yellowing.

The following example illustrates the effectiveness of the treatment bath in protecting prints from the effect of external strong sulfiding agents.

EXAMPLE 7 Photographic prints prepared and processed in the manner used in Example 2 were soaked for 3 minutes in a 0.2% sodium sulfide solution before drying. These treated prints were not stained by such exposure to a strong sulfiding agent.

Tests made on prints giventhe treatment of our invention have shown that without exception, fungal attack was reduced to a minimum and in many cases prevented entirely. The loss of the quaternary ammonium compound from the treated photographic element appears to proceed at an extremely low rate, thus insuring good protection of long exposure periods.

The treatment baths are equally effective when used on either projection or contact prints. When double-weight ments against chemical deterioration and microbiological attack under tropical storage conditions. The treatment consists of giving the photographic element being processed a short wash following the fixing bath with a 5 to 10 minute soak in an aqueous solution containing preferably from .25 to 2.0% of the quaternary ammonium salt before drying. Black-and-white prints or films containing appreciable amounts of residual thiosulfate compounds but which have been given the stabilizing and fungicidal treatment will not fade or yellow when stored under tropical conditions for prolonged periods and fungicidal attack is minimized and often prevented. This treatment is not only much more effective than prior art processes but is convenient and simple. For example, multiple fixing baths, prolonged washing, or the use of toxic, unstable chemicals such as potassium permanganate, iodine, hydrogen peroxide and others are not needed in our process.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it 7 will be understood that variations and modifications can be effected within the spiritand the scope of the invention as described hereinabove and as defined inthe appended claims.

We claim:

1. A process in which a developed and fixed silver image in a photographic element is (1) treated in an aqueous solution containing at least 0.25 percent by weight of a compound selected from the group consisting of surface active compounds of the formula:

i/ nioonorocnnz-l t-(cnz) and wherein R and R each represents an alkyl radical having from 6 to 20 carbon atoms; R and R each represents a member selected from the group consisting of a hydrogen atom and a lower alkyl group having from 1 to 6 carbon atoms; n is an integer of 0 to 3; and Z is a halogen atom; and (2) then drying the treated element.

2. A process in which a developed and fixed silver image in a photographic element is (1) treated in an aqueous solution containing at least 0.25 percent by weight of diisobutyl phenoxy ethoxy ethyl dimethyl benzyl ammonium chloride; and (2) is then dried.

3. A process in which a developed and fixed silver image in a photographic element is (1) treated in an aqueous solution containing at least 0.25 percent by weight of diisobutyl cresoxy ethoxy ethyl dimethyl benzyl ammonium chloride; and (2) is then dried.

4. A process in which a developed and fixed silver image in a photographic element is (1) treated in an aqueous solution containing at least 0.25 percent by weight of a surface active compound of the formula:

wherein R is an alkyl radical having from 6 to 20 carbon atoms and Z is a halogen atom; and (2) is then dried.

5. A process in which a developed and fixed silver image in a photographic element is (1) treated in an aqueous solution containing at least 0.25 percent by weight of lauryl pyridiniurn chloride; and (2) is then dried.

6. A process in which a developed and fixed silver image in a photographic element is 1) treated in an aqueous solution containing at least 0.25 percent by weight of cetyl pyridinium chloride; and (2) is then dried. 7. A process in which a developed and fixed silver image in a photographic element is (1) treated in an aqueous solution containing at least 0.25 percent by weight of a surface active compound of the formula:

l R1N and wherein R, R R and R are members selected from the group consisting of alkyl, aryloxyalkyloxyalkyl, aryl, and arylalkyl radicals, said radicals represented by R having 6 to 20 carbon atoms and said radicals represented by R R and R having 1 to 20 carbon atoms; and Z is a member selected from the group consisting of halogen atoms, sulfate radicals, and acetate radicals; and (2) is then dried.

References Cited in the file of this patent UNITED STATES PATENTS 1,892,725 Griessbach et a1. Jan. 3, 1933 2,271,623 Carroll Feb. 3, 1942 2,295,504 Shelton Sept. 8, 1942 2,566,132 Littler Aug. 28, 1951 FOREIGN PATENTS 459,681 Canada Sept. 13, 1949 OTHER REFERENCES Lawrence: Surface-Active Quaternary Ammonium Germicides, Academic Press, New York (1950), pages 198, 202.

Rohm and Haas: Hyamines 1622 and 10-X, copyright 1947, released January 28, 1948.

Clerc: Photography, Theory and Practice, Pitman and Sons, New York, 1937, page 291. 

7. A PROCESS IN WHICH A DEVELOLPED AND FIXED SILVER IMAGE IN A PHOTOGRAPHIC ELEMENT IS (1) TREATED IN AN AQUEOUS SOLUTION CONTAINING AT LEAST 0.25 PERCENT BY WEIGHT OF A SURFACE ACTIVE COMPOUND OF THE FORMULA: 